A 19-year-old girl has died in Costa Rica due to a parasitic disease caused by the larvae of a carnivorous fly. This is the first human victim. Known in English New World Screwworm (literally New World vine worm in reference to its larval state and the fact that like screws they can penetrate deeply), these «killer flies» (scientifically Cochliomya hominivorax) generally attack livestock and domestic animals and rarely humans. Flesh flies lay their eggs inside open wounds of any species of warm-blooded animal. Within a few hours the eggs hatch, giving rise to small larvae that feed on the surrounding tissue, causing a parasitic disease known as miasis with painful infectionstissue loss, up to death, in some cases.
Seven cases of human infection
The woman who died in Costa Rica had a series of chronic conditions that compromised her recovery. «The young woman had a lesion in the mouth where larvae of the Cochliomyia hominivorax fly were detected” reported Dr. María Luisa Ortiz, Director General of Health. According to the Ministry of Health in Costa Rica the symptoms in humans can include pain, intense itching, skin rash, skin nodules, bumps on the skin.
The state of emergency
In April 2024 the Central American country declared it state of emergency due to the massive presence of carnivorous flies. They have since been reported seven cases of human infestation: all recovered except for the latter. What makes these flies particularly dangerous is that, unlike other species, they prefer to lay their eggs on the wounds of living mammals rather than on carrion (each fly can lay between 100 and 350 eggs). The eggs hatch in less than 24 hours and the larvae penetrate the wound. It is easy for the infestation to spread between various animals living in groups (often herds of cattle) because the smell of an infested wound attracts other egg-bearing female flies. If left untreated, infestations can kill an animal within one to two weeks.
Work to eradicate the insect
The carnivorous fly, with the blue-green body and orange eyes, was first reported in 1858 in Guyana. Costa Rica declared it had permanently eradicated the insect in 2000, but the killer fly reappeared last year. In the United States, a massive eradication campaign that lasted decades using the sterile insect technique proved successful and almost eliminated the species that had infested herds of livestock in Florida for a long time.
